In an effort to discover new ways to fight the swine flu, the Public Health Agency of Canada intends to test the blood of people contracting the ailment to check their vitamin D levels.
The agency is taking the unconventional action to try to find out whether those with mild cases of the flu have more of the sunshine vitamin circulating in their bodies than those who develop severe or even deadly reactions to the H1N1 virus.
If researchers determine that the vitamin protects against the swine flu, it will give health authorities another line of attack against the pandemic, besides such common-sense approaches as large-scale vaccinations and hand-washing campaigns.
A finding of a link to the vitamin would mean that people could reduce the odds of being harmed by the new flu bug by simply popping a low-cost supplement that is widely available at almost every drugstore.
Scientists have long been wondering about a possible connection between vitamin D and influenza because of the striking observations in both the northern and southern hemispheres that flu is mostly a wintertime ailment. This is the period each year when sunshine isn't intense enough to allow people to make the vitamin the natural way - in naked skin exposed to ultraviolet light - causing levels of the nutrient to plunge among those not taking supplements.
The public health agency confirmed the vitamin D research in an e-mail to The Globe in response to questions about the testing.
"Epidemiological evidence suggests a role for vitamin D in seasonal influenza," the agency said, adding that the low amounts of the nutrient in the winter "appear to correlate with the occurrence of seasonal influenza."
The annual pattern of influenza - bad in winter and rare in summer - is the reason many health experts are worried that the swine flu epidemic, now running at relatively modest infection rates, will go into overdrive starting in the fall.
The federal health agency cautioned that a causal relationship between not having a lot of vitamin D and the risks posed by the flu remains to be proved, but is said the approach may offer promise in reducing the severity of infections.
A number of university and hospital researchers, in conjunction with the agency, started investigating the possible role of vitamin D and the severity of flu symptoms last year, well before the current outbreak began in Mexico this spring.
But the agency said it has adapted this continuing study to the H1N1 outbreak. As part of the research, the investigators will also look at whether a person's genetic makeup has something to do with the intensity of the flu they experience.
Although not much is known about the ability of vitamin D to mitigate the effects of the swine flu, the agency is citing one tantalizing piece of research suggesting the approach is more than a long shot and actually holds promise in combatting the new pandemic.
In the 1940s, researchers experimenting with mice found that those receiving diets low in vitamin D were more susceptible to an experimental swine-flu infection than those that received adequate amounts of the nutrient, according to the e-mail from the agency.
The reason vitamin D might be able to fight the flu isn't known, but the prevailing hypothesis is that the nutrient is able to strengthen the immune system, allowing those infected to better fight off their illness. Vitamin D has been found, for instance, to offer some protection against tuberculosis.
"The evidence is almost overwhelming that vitamin D appears to be making the immune system attack foreign entities better," said Reinhold Vieth, a professor in the department of nutritional sciences at the University of Toronto.
He said the agency's research on H1N1 severity and vitamin D levels "bodes really well" for figuring out whether the nutrient can be used to help combat the virus.
The agency said that the way the nutrient might protect against the flu "is not fully understood," but it said new research "suggests that vitamin D induces the production of antimicrobial substances in the body that possess neutralizing activity against a variety of infectious agents, including the influenza virus."